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RT5924A
16-CH Constant Current Sink LED Driver
General Description
Features
The RT5924A is a constant current LED driver for LED
display applications. The driver integrates a 16-bit shift
register, a 16-bit latch, a constant current control block
and a inrush output current control block.

16 Constant Current Output Channels

Constant Output Current Invariant to Load Voltage
Change
Pre-charge Function for Ghosting Eliminating
Low Gray Compensation
Constant Output Current Range :
 3mA to 45mA @ VDD = 5V
 3mA to 30mA @ VDD = 3.3V
Maximum Constant Current Output Voltage : 14V
Constant Output Current Accuracy :
 Between Channels : <±
±1.5% (typ.); <±
±2.5% (max.)
Constant Output Current Accuracy :
 Between ICs : <±
±2.5% (typ.); <±
±3% (max.)
Adjustable Output Current Through an External
Resistor
Fast Response of Output Current, OE (typ.) : 30ns
Maximum Data Transfer Frequency : 30MHz
Power Supply Voltage : 3.3V and 5V
RoHS Compliant and Halogen Free
The 16-bit shift register can shift out input serial data to
SDO output pin with 30MHz maximum frequency. The
16-bit latch block can latch input data. As the LE pin is
high, the PWM data in the latch is changed. The constant
current control block ensures the differences of output
currents between channels and between ICs are smaller
than ±2.5% and ±3%, respectively. The output current value
is determined by an external resistor. The range of the
constant current output is 3mA to 45mA.






Ordering Information

RT5924A
Package Type
S : SOP-24 (236mil)
A : SSOP-24
QW : WQFN-24L 4x4 (W-Type)
(Exposed Pad-Option 1)
Lead Plating System
G : Green (Halogen Free and Pb Free)



Application

Note :

Richtek products are :


RoHS compliant and compatible with the current require-

Outdoor LED Video Displays
Indoor LED Video Displays
LED Message Boards
LED Message Signs
ments of IPC/JEDEC J-STD-020.

Suitable for use in SnPb or Pb-free soldering processes.
Simplified Application Circuit
VLED
......
VDD
CIN
VOUT0 VOUT1 VOUT15
VDD
R-EXT
RT5924A
OE
LE
REXT
CLK
SDI
SDO
GND
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
DS5924A-00
September 2015
is a registered trademark of Richtek Technology Corporation.
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1
RT5924A
Marking Information
RT5924AGS
RT5924AGQW
RT5924AGS : Product Number
RT5924A
GSYMDNN
YMDNN : Date Code
2B= : Product Code
2B=YM
DNN
YMDNN : Date Code
RT5924AGA
RT5924AGA : Product Number
RT5924A
GAYMDNN
YMDNN : Date Code
Pin Configurations
24
2
23
3
22
4
21
5
20
6
19
7
18
8
17
9
16
10
15
11
14
12
13
VDD
R-EXT
SDO
OE
VOUT15
VOUT14
VOUT13
VOUT12
VOUT11
VOUT10
VOUT9
VOUT8
SOP-24 (236mil) / SSOP-24
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2
24 23 22 21 20 19
LE
VOUT0
VOUT1
VOUT2
VOUT3
VOUT4
1
18
2
17
3
16
GND
4
15
25
5
14
13
6
7
8
VOUT15
VOUT14
VOUT13
VOUT12
VOUT11
VOUT10
9 10 11 12
VOUT5
VOUT6
VOUT7
GND
VOUT8
VOUT9
GND
SDI
CLK
LE
VOUT0
VOUT1
VOUT2
VOUT3
VOUT4
VOUT5
VOUT6
VOUT7
CLK
SDI
VDD
R-EXT
OE
SDO
(TOP VIEW)
WQFN-24L 4x4
is a registered trademark of Richtek Technology Corporation.
DS5924A-00
September 2015
RT5924A
Functional Pin Description
Pin No.
Pin Name
SOP-24 (236mil),
WQFN-24L 4x4
SSOP-24
1
10
GND
2
3
23
24
SDI
CLK
4
1
LE
5 to 20
2 to 9, 11 to 18
20
OE
22
19
SDO
23
21
R-EXT
24
22
VDD
25 (Exposed Pad) GND
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
DS5924A-00
September 2015
Ground. The ground pin is used for control logic and
current sink circuit.
Serial Data Input.
Clock for Serial Data Transfer Input.
Data Latch Input. When the LE is high, the serial data
is saved at the output latch. When the LE is low, the
data is kept as last state.
VOUT0 to VOUT15 Constant Current Output with Sink Type.
21
--
Pin Function
Constant Current Output Enable/Disable Control
Input :
Enabled the output drivers when the OE input is low.
Disabled the output drivers when the OE input is high.
Serial Data Output.
Constant Current Setting. Connect an external resistor
to set the LED current.
Power Supply Input.
Ground. The exposed pad must be soldered to a large
PCB and connected to GND for maximum power
dissipation.
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RT5924A
Function Block Diagram
VOUT0
VOUT1
VOUT14
VOUT15
VDD
......
VDD
OE
Bandgap
Constant Current Control Circuit
......
LE
VDD
R-EXT
16 bit Data Latch
GND
......
SDI
16 bit Shift Register
SDO
CLK
Operation
The RT5924A is a constant current LED driver for the LED
display applications. The driver integrates a 16-bit shift
register, a 16-bit data latch, a constant current control
circuit and an inrush output current control block.
The inrush output current control block is consisted of
delay circuits. The delay circuits can turn on the output
to reduce the inrush current as the OE pin is enabled.
16-bit Shift Register
Typical Operation
As shown in the Typical Application Circuit, the LED driver
IC RT5924A can be connected in series. The input control
signal : OE, LE, and CLK come from CPU. The serial
data can be transferred from the SDI pin to the SDO output
pin. Then, the output data of SDO pin sends the data to
next RT5924A SDI input pin to transfer data in series. The
serial data can be converted to parallel data to drive the
output port.
The 16-bit shift register has two functions. One is to shift
the input serial data to the SDO output pin. The other is
to save the serial signal to the parallel output signal to
drive the output channel.
Constant Current Control Circuit
The constant current control circuit can make sure the
accuracy between channels and between ICs. The output
current value is determined by an external resistor as
shown in below :
IOUT = 1.24  (1/ REXT )  15
REXT = (1.24 / IOUT )  15
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is a registered trademark of Richtek Technology Corporation.
DS5924A-00
September 2015
RT5924A
Absolute Maximum Ratings












(Note 1)
Supply Voltage, VDD ----------------------------------------------------------------------------------------------------Output Current, IOUT -----------------------------------------------------------------------------------------------------Output Voltage, VOUTx ---------------------------------------------------------------------------------------------------Clock Frequency, FCLK --------------------------------------------------------------------------------------------------GND Terminal Current, IGND --------------------------------------------------------------------------------------------Other Pins ------------------------------------------------------------------------------------------------------------------Power Dissipation, PD @ TA = 25°C
SOP-24 (236mil) ----------------------------------------------------------------------------------------------------------SSOP-24 -------------------------------------------------------------------------------------------------------------------WQFN-24L 4x4 -----------------------------------------------------------------------------------------------------------Package Thermal Resistance (Note 2)
SOP-24 (236mil), θJA ----------------------------------------------------------------------------------------------------SSOP-24, θJA -------------------------------------------------------------------------------------------------------------WQFN-24L 4x4, θJA ------------------------------------------------------------------------------------------------------WQFN-24L 4x4, θJC -----------------------------------------------------------------------------------------------------Junction Temperature ----------------------------------------------------------------------------------------------------Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------------Storage Temperature Range -------------------------------------------------------------------------------------------ESD Susceptibility (Note 3)
HBM (Human Body Model) ----------------------------------------------------------------------------------------------
Recommended Operating Conditions



−0.3V to 6V
45mA
−0.5V to 14V
30MHz
720mA
−0.3V to VDD
1.15W
0.92W
3.57W
86.5°C/W
108.2°C/W
28°C/W
7°C/W
150°C
260°C
−65°C to 150°C
8kV
(Note 4)
Supply Voltage, VDD ----------------------------------------------------------------------------------------------------- 3V to 5.5V
Junction Temperature Range -------------------------------------------------------------------------------------------- −40°C to 125°C
Ambient Temperature Range -------------------------------------------------------------------------------------------- −40°C to 85°C
Electrical Characteristics
Electrical Characteristics (DC)
(VDD = 5V, TA = 25°C, unless otherwise specified)
Parameter
Supply Voltage
Output Current
Input Voltage
Symbol
Test Conditions
VDD
Typ
Max
Unit
4.5
5
5.5
V
IOUT
DC Test Circuit
3
--
45
IOH
SDO
--
--
1
IOL
SDO
--
--
1
High-level VIH
TA = 40C to 85C
0.7VDD
--
VDD
Low-level VIL
TA = 40C to 85C
GND
--
0.3VDD
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
DS5924A-00
Min
September 2015
mA
V
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RT5924A
Parameter
Symbol
Test Conditions
Min
Typ
Max
4.6
--
--
--
--
0.4
Unit
V OH
IOH = 1mA
V OL
IOL = 1mA
Output Current 1
IOUT1
V DS = 1V
R EXT = 6000
--
3.1
--
mA
Current Skew
dIOUT1
IOL = 3.1mA, VDS = 1V
R EXT = 6000
--
±1.5
±2.5
%
Output Current 2
IOUT2
V DS = 1V
R EXT = 720
--
25.8
--
mA
Current Skew
dIOUT2
IOL = 25.8mA, V DS = 1V R EXT = 720
--
±1.5
±2.5
%
Output Current vs. Output
%/dVDS
Voltage Regulation
VDS within 1V and 3V
--
±0.5
±1
%/V
Output Current vs. Supply
%/dVDD
Voltage Regulation
V DD within 4.5V and 5.5V
--
±0.1
±1
%/V
Pull-Up Resistor
RIN(Up)
OE
250
500
800
k
Pull-Down Resistor
RIN(Down)
LE
250
500
800
k
IDD(off) 1
R EXT = Open, VOUT0 to VOUT15 = Off
--
2
2.8
IDD(off) 2
R EXT = 1240, VOUT0 to VOUT15 = Off
--
4
4.8
IDD(off) 3
R EXT = 620, VOUT0 to VOUT15 = Off
--
6
6.8
IDD(on)
1
R EXT = 1240, VOUT0 to VOUT15 = On
--
5.2
8.2
IDD(on)
2
R EXT = 620, VOUT0 to VOUT15 = On
--
6.5
9.5
Min
Typ
Max
Unit
3
3.3
4.5
V
Output Voltage
SDO
“OFF”
Supply Current
“ON”
V
mA
VR-EXT = 1.24V; IOUT = (V R-EXT / REXT) x 15
Electrical Characteristics (DC)
(VDD = 3.3V, TA = 25°C, unless otherwise specified)
Parameter
Supply Voltage
Symbol
Test Conditions
V DD
Output Current
IOUT
DC Test Circuit
3
--
30
IOH
SDO
--
--
1
IOL
SDO
--
--
1
mA
High level VIH
TA = 40C to 85C
0.7VDD
--
VDD
Low level VIL
TA = 40C to 85C
GND
--
0.3V DD
V OH
IOH = 1mA
2.9
--
--
V OL
IOL = 1mA
--
--
0.4
Output Current 1
IOUT1
V DS = 1V
R EXT = 6000
--
3.1
--
mA
Current Skew
dIOUT1
IOL = 3.1mA, V DS = 1V
R EXT = 6000
--
±1.5
±2.5
%
Output Current 2
IOUT2
V DS = 1V
R EXT = 720
--
25.8
--
mA
Current Skew
dIOUT2
IOL = 25.8mA, VDS = 1V R EXT = 720
--
±1.5
±2.5
%
Input Voltage
Output Voltage SDO
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V
V
is a registered trademark of Richtek Technology Corporation.
DS5924A-00
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RT5924A
Parameter
Symbol
Test Conditions
Min
Typ
Max
Unit
Output Current vs. Output
Voltage Regulation
%/dVDS
VDS within 1V and 3V
--
±0.5
±1
%/V
Output Current vs. Supply
Voltage Regulation
%/dVDD
VDD within 3V and 3.6V
--
±0.1
±1
%/V
Pull-Up Resistor
RIN(Up)
OE
250
500
800
k
Pull-Down Resistor
RIN(Down)
LE
250
500
800
k
IDD(off) 1
REXT = Open, VOUT0 to VOUT15 = Off
--
1.7
2.3
IDD(off) 2
REXT = 1851, VOUT0 to VOUT15 = Off
--
3.9
4.5
IDD(off) 3
REXT = 748, VOUT0 to VOUT15 = Off
--
5.2
5.8
IDD(on) 1
REXT = 1851, VOUT0 to VOUT15 = On
--
3.9
4.5
IDD(on) 2
REXT = 748, VOUT0 to VOUT15 = On
--
5.2
5.8
Min
Typ
Max
Unit
“OFF”
Supply Current
“ON”
mA
VR-EXT = 1.24V; IOUT = (VR-EXT / REXT) x 15
Electrical Characteristics (AC)
(VDD = 5V, TA = 25°C, unless otherwise specified)
Parameter
Propagation
Delay Time
(“L” to “H”)
Propagation
Delay Time
(“H” to “L”)
Pulse Width
Symbol
Test Conditions
LE  VOUTn
tpLH1
--
12
30
ns
OE  VOUTn
tpLH2
--
12
30
ns
CLK  SDO
tpLH
--
8
20
ns
LE  VOUTn
tpHL1
--
12
30
ns
OE  VOUTn
tpHL2
--
12
30
ns
CLK  SDO
tpHL
--
8
20
ns
CLK
tw(CLK)
20
--
--
ns
LE
tw(L)
20
--
--
ns
OE
tw(OE)
30
--
60
ns
30
--
--
ns
5
--
--
ns
5
--
--
ns
3
--
--
ns
VDD = 5V
VDS = 1V
VIH = VDD
VIL = GND
REXT = 930
VL = 4.5V
RL = 162
CL = 10pF
Hold Time for LE
th(L)
Setup Time for LE
tsu (L)
Hold Time for SDI
th(D)
Setup Time for SDI
tsu (D)
Maximum CLK Rising Time
tr
--
--
500
ns
Maximum CLK Falling Time
tf
--
--
500
ns
SDO Rising Time
tr,SDO
--
5
12
ns
SDO Falling Time
Output Rising Time of VOUT (turn
off)
Output Falling Time of VOUT (turn
on)
Tf,SDO
--
5
12
ns
tor
--
10
30
ns
tof
--
10
30
ns
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
DS5924A-00
September 2015
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RT5924A
Electrical Characteristics (AC)
(VDD = 3.3V, TA = 25°C, unless otherwise specified)
Parameter
Propagation
Delay Time
(“L” to “H”)
Propagation
Delay Time
(“H” to “L”)
Pulse Width
Symbol
Test Conditions
Min
Typ
Max
Unit
LE  VOUTn
tpLH1
--
12
30
ns
OE  VOUTn
tpLH2
--
12
30
ns
CLK  SDO
tpLH
--
8
20
ns
LE  VOUTn
tpHL1
--
12
30
ns
OE  VOUTn
tpHL2
--
12
30
ns
CLK  SDO
tpHL
--
8
20
ns
CLK
tw(CLK)
20
--
--
ns
LE
tw(L)
20
--
--
ns
OE
tw(OE)
30
--
60
ns
30
--
--
ns
5
--
--
ns
5
--
--
ns
3
--
--
ns
VDD = 3.3V
VDS = 1V
VIH = VDD
VIL = GND
REXT = 930
VL = 3V
RL = 100
CL = 10pF
Hold Time for LE
th(L)
Setup Time for LE
tsu (L)
Hold Time for SDI
th(D)
Setup Time for SDI
tsu (D)
Maximum CLK Rising Time
tr
--
--
500
ns
Maximum CLK Falling Time
tf
--
--
500
ns
SDO Rising Time
tr,SDO
--
5
12
ns
SDO Falling l Time
Tf,SDO
--
5
12
ns
Output Rising Time of VOUT (turn off)
tor
--
10
30
ns
Output Falling Time of VOUT (turn on)
tof
--
10
30
ns
Note 1. Stresses beyond those listed “Absolute Maximum Ratings” may cause permanent damage to the device. These are
stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in
the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions may
affect device reliability.
Note 2. θJA is measured at TA = 25°C on a high effective thermal conductivity four-layer test board per JEDEC 51-7. θJC is
measured at the exposed pad of the package.
Note 3. Devices are ESD sensitive. Handling precaution is recommended.
Note 4. The device is not guaranteed to function outside its operating conditions.
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is a registered trademark of Richtek Technology Corporation.
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RT5924A
Typical Application Circuit
VLED
VLED
......
VDD
VOUT0 VOUT1
......
VDD
VOUT15
VOUT0 VOUT1
VDD
CIN
CIN
R-EXT
R-EXT
GND
OE
REXT
VOUT15
VDD
GND
OE
REXT
LE
......
LE
CLK
CLK
SDO
SDI
SDO
SDI
3
Test Circuit
for DC Characteristics
RT5924A
SDI
CLK
LE
VIH = VDD
VIL = 0
VDD
OE
IOUT0
SDO
VOUT0
..
..
..
CL
R-EXT
IREF
IDD
VDD
16ch
VL
VOUT15
GND
REXT
IOUT15
VL
..
..
..
for AC Characteristics
RT5924A
Function
Generator
SDI
CLK
LE
VDD
VDD
OE
VIH = VDD, VIL = 0
tr = tf =10ns
SDO
(10% to 90%)
CL
R-EXT
IREF
REXT
GND
IDD
RL
IOUT0
VL
VOUT0
..
..
..
CL
RL
IOUT15
..
..
..
16ch
VL
VOUT15
CL
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September 2015
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RT5924A
Timing Diagram
N=0
CLK
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15
SDI
LE
OE
OFF
ON
OFF
ON
OFF
ON
OFF
ON
VOUT0
VOUT1
VOUT2
VOUT3
OFF
ON
VOUT15
SDO
: don´t care
tW(CLK)
CLK 50%
50%
SDO
tW(L)
tpLH, tpHL
LE
OE
50%
50%
50%
50%
Low = Outputs Enabled
High = Output OFF
50%
VOUTx
tpLH1, tpHL1
Low = Output On
tpLH2, tpHL2
tW(OE)
OE
50%
50%
tpHL3
VOUTn
tpLH3
90%
50%
10%
tof
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90%
50%
10%
tor
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DS5924A-00
September 2015
RT5924A
Table 1. Truth Table
CLK
LE
OE
SDI
VOUT0…VOUT7…VOUT15
SDO

H
L
Dn
Dn …Dn-7 …Dn-15
Dn-15

L
L
Dn+1
No Change
Dn-14

H
L
Dn+2
Dn+2 …Dn-5 …Dn-13
Dn-13

X
L
Dn+3
Dn+2 …Dn-5 …Dn-13
Dn-13

X
H
Dn+3
Off
Dn-13
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RT5924A
Typical Operating Characteristics
Output Current vs. Temperature
Output Current vs. R-EXT
50
26.5
VDS = 1V, VDD = 5V, REXT = 400Ω to 6000Ω
REXT = 720Ω
40
Output Current (mA)
Output Current (mA)
26.4
30
20
10
26.3
VDD = 5V
26.2
VDD = 3.3V
26.1
26.0
25.9
25.8
0
25.7
0
1000
2000
3000
4000
5000
6000
-50
-25
25
50
75
100
125
Temperature (°C)
R-EXT
R-EXT (Ω)
(Ω)
Output Current vs. Output Voltage
Output Current vs. Output Voltage
50
50
45
40
35
30
25
20
15
10
40
35
30
25
20
15
10
5
5
0
0
0.0
0.5
1.0
1.5
2.0
2.5
VDD = 3.3V, REXT = 400Ω to 6000Ω
45
VDD = 5V, REXT = 400Ω to 6000Ω
Output Current (mA)
Output Current (mA)
0
0.0
3.0
0.5
1.0
1.5
2.0
2.5
Output Voltage (V)
Output Voltage (V)
Constant-Current Output Voltage
Constant-Current Output Voltage
OE
(3V/Div)
OE
(3V/Div)
CH0
(2V/Div)
CH8
(2V/Div)
CH7
(2V/Div)
CH15
(2V/Div)
VDS =ENB
1V, =VDD
= 5V, OE
= 30ns,TCAP
REXT == 720Ω
VIN = 12V,
1, VSEL
= [0,0,0,0],
39nF
Time (10ns/Div)
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3.0
VDS = 1V, VDD = 5V, OE = 30ns, REXT = 720Ω
Time (10ns/Div)
is a registered trademark of Richtek Technology Corporation.
DS5924A-00
September 2015
RT5924A
Application Information
There are two types of application circuit for connecting
LED and the RT5924A are shown as follows. In traditional
connection type, use the same color and type for LED
connecting to RT5924A. Generally, the supply voltage is
fixed in this application. VLED must be higher than the
LED forward voltage and output voltage (VDS) of RT5924A.
When operating RGB LED display system, it is suggested
to use different supply voltages for different color LED sets.
This topology can reduce the output voltage of the LED
driver to improve the power efficiency.
Inadequate VDD can cause timing problems, and very noisy
LED supplies can affect LED current regulation. It is
recommended to place an additional electrolytic capacitor
CLED closed to LED for better output current regulation.
......
RT5924A
MicroSDI
SDO
SDI
controller
LE OE CLK
......
CLED
RT5924A
SDO
SDI
LE OE CLK
Constant Current
The RT5924A provides less current variations from channel
to channel and from IC to IC in LED display system. The
maximum constant current accuracy between channels
is less than ±2.5%, and is less than ±3% between ICs.
No matter the variations of LED forward voltages (Vf), the
output current can be kept constant.
VLED Operation Range
Due to the limitation of the package power dissipation, it
is suitable for the RT5924A to operate in the VDS range
from 0.8V to 2V. Higher VDS will cause more power
consumption and thermal.
In this case, it is suggested to reduce the supply voltage
level. Alternative method is to use a resister or a Zener
diode in series with the LED to reduce the voltage of VDS.
as shown in the following figures.
Voltage
Supply
Voltage
Supply
......
RT5924A
SDO
SDI
LE OE CLK
......
Zener Diode
CLED
RT5924A
SDO
SDI
LE OE CLK
......
VLED
......
VDC Vf
Vf
VDC
Figure 1. Traditional Application Circuit
RT5924A
......
Microcontroller
SDI _R
RT5924A
SDO
SDI
LE OE CLK
......
RT5924A
CLED
RT5924A
SDO
SDI
LE OE CLK
VLED_R
Figure 3. Alternative Method to Reduce the VDS
Maximum Output Current
......
SDI _G
RT5924A
SDO
SDI
LE OE CLK
......
RT5924A
SDO
SDI
LE OE CLK
CLED
VLED_G
The power dissipation (PD) is different due to different
packages. The power dissipation can be determined by
the formula :
PD = (TJ − TA)/Rth(J-A)
......
SDI _B
RT5924A
SDO
SDI
LE OE CLK
......
RT5924A
SDO
SDI
LE OE CLK
CLED
VLED_B
When 16 output channels are activated, the power
dissipation of IC is :
PD = (IDD x VDD) + (IOUT x Duty x VDS x 16).
Figure 2. Power Saving for RGB LED Application
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RT5924A
IOUT = {[( TJ − TA)/Rth(J-A)] − (IDD x VDD)} / VDS / Duty / 16,
Where T J is the recommended operating junction
temperature (125°C) and TA is ambient temperature. When
ambient temperature increases, the allowed maximum
output current decreases.
Thermal Considerations
For continuous operation, do not exceed absolute
maximum operation junction temperature. The maximum
power dissipation depends on the thermal resistance of
IC package, PCB layout, the rate of surroundings airflow
and temperature difference between junction to ambient.
The maximum power dissipation can be calculated by
following formula :
The maximum power dissipation depends on the operating
ambient temperature for fixed T J(MAX) and thermal
resistance, θJA. The derating curve in Figure 4 of derating
curves allows the designer to see the effect of rising
ambient temperature on the maximum power dissipation
allowed.
4.0
Maximum Power Dissipation (W)1
The power dissipation should be less than the maximum
power dissipation. So the maximum output current can
be calculated by the following equation.
For recommended operating condition specifications, the
maximum junction temperature is 125°C. The junction to
ambient thermal resistance θJA is layout dependent. For
SOP-24 (236mil) package, the thermal resistance θJA is
86.5°C/W on the standard JEDEC 51-7 four-layer thermal
test board. For SSOP-24 package, the thermal resistance
θJA is 108.2°C/W on the standard JEDEC 51-7 four-layer
thermal test board. For WQFN-24L 4x4 package, the
thermal resistance θJA is 28°C/W on the standard JEDEC
51-7 four-layer thermal test board. The maximum power
dissipation at TA = 25°C can be calculated by following
formula :
PD(MAX) = (125°C − 25°C) / (86.5°C/W) = 1.15W for
SOP-24 (236mil) package
WQFN-24L 4x4
3.2
2.8
2.4
2.0
1.6
SOP-24 (236mil)
1.2
0.8
SSOP-24
0.4
0.0
0
25
50
75
100
125
Ambient Temperature (°C)
PD(MAX) = ( TJ(MAX) − TA ) / θJA
Where T J(MAX) is the maximum operation junction
temperature, TA is the ambient temperature and the θJA is
the junction to ambient thermal resistance.
Four-Layer PCB
3.6
Figure 4. Derating Curve of Maximum Power Dissipation
Layout Considerations
For best performance of RT5924A, please abide by the
following layout guide.

The capacitor CVDD and external resistor REXT must be
placed as close as possible to the VDD and R-EXT pins
of the device respectively.

The GND should be connected to a strong ground plane.

Do not use thin and long wires to present the parasitical
inductance from influencing the LED operation.

Keep the main current traces as possible as short and
wide

Place the capacitor CLED as close as possible to the
LED set for better current regulation.
PD(MAX) = (125°C − 25°C) / (108.2°C/W) = 0.92W for
SSOP-24 package
P D(MAX) = (125°C − 25°C) / (28°C/W) = 3.57W for
WQFN-24L 4x4 package
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is a registered trademark of Richtek Technology Corporation.
DS5924A-00
September 2015
RT5924A
Place the resistor REXT to the
R-EXT as close as possible .
GND
CVDD
VOUT8
VOUT9
VOUT11
VOUT10
VOUT12
VOUT13
VOUT14
VOUT15
OE
SDO
R-EXT
VDD
REXT
24 23 22 21 20 19 18 17 16 15 14 13
GND
9
CLED
10 11 12
VOUT6
VOUT7
8
VOUT5
7
VOUT4
6
VOUT3
5
VOUT1
VOUT2
4
VOUT0
3
LE
SDI
GND
2
CLK
Place the
capacitor
CVDD to the
VDD as close
as possible.
VLED
Place the
capacitor
CLED to the
VLED as close
as possible.
Figure 5. PCB Layout Guide for SOP-24 (236mil) / SSOP-24
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
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15
RT5924A
Outline Dimension
H
A
M
J
B
F
C
I
D
Dimensions In Millimeters
Dimensions In Inches
Symbol
Min
Max
Min
Max
A
12.800
13.200
0.504
0.520
B
5.800
6.200
0.228
0.244
C
1.350
1.900
0.053
0.075
D
0.300
0.520
0.012
0.020
F
1.000
0.040
H
0.100
0.270
0.004
0.011
I
0.050
0.150
0.002
0.006
J
7.700
8.300
0.303
0.327
M
0.250
0.650
0.010
0.026
24–Lead SOP Plastic Package (Body Width = 236mil)
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is a registered trademark of Richtek Technology Corporation.
DS5924A-00
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RT5924A
c
D
L
E
E1
e
A2
A
A1
b
Dimensions In Millimeters
Dimensions In Inches
Symbol
Min
Max
Min
Max
A
1.346
1.753
0.053
0.069
A1
0.100
0.254
0.004
0.010
A2
1.370
1.520
0.054
0.060
b
0.203
0.305
0.008
0.012
C
0.178
0.254
0.007
0.010
D
8.530
8.740
0.336
0.344
e
0.635
0.025
E
5.800
6.200
0.228
0.244
E1
3.800
4.000
0.150
0.157
L
0.380
1.270
0.015
0.050
24-Lead SSOP Plastic Package
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
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September 2015
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17
RT5924A
D2
D
SEE DETAIL A
L
1
E
E2
e
b
A3
Symbol
D2
E2
1
2
DETAIL A
Pin #1 ID and Tie Bar Mark Options
A
A1
1
2
Note : The configuration of the Pin #1 identifier is optional,
but must be located within the zone indicated.
Dimensions In Millimeters
Dimensions In Inches
Min
Max
Min
Max
A
0.700
0.800
0.028
0.031
A1
0.000
0.050
0.000
0.002
A3
0.175
0.250
0.007
0.010
b
0.180
0.300
0.007
0.012
D
3.950
4.050
0.156
0.159
Option 1
2.400
2.500
0.094
0.098
Option 2
2.650
2.750
0.104
0.108
E
3.950
4.050
0.156
0.159
Option 1
2.400
2.500
0.094
0.098
Option 2
2.650
2.750
0.104
0.108
e
L
0.500
0.350
0.020
0.450
0.014
0.018
W-Type 24L QFN 4x4 Package
Richtek Technology Corporation
14F, No. 8, Tai Yuen 1st Street, Chupei City
Hsinchu, Taiwan, R.O.C.
Tel: (8863)5526789
Richtek products are sold by description only. Richtek reserves the right to change the circuitry and/or specifications without notice at any time. Customers should
obtain the latest relevant information and data sheets before placing orders and should verify that such information is current and complete. Richtek cannot
assume responsibility for use of any circuitry other than circuitry entirely embodied in a Richtek product. Information furnished by Richtek is believed to be
accurate and reliable. However, no responsibility is assumed by Richtek or its subsidiaries for its use; nor for any infringements of patents or other rights of third
parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Richtek or its subsidiaries.
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DS5924A-00
September 2015
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